Phytoplankton ecology and production in the Red Sea off Jiddah,Saudi Arabia

Phytoplankton species diversity was generally high throughout the year at two stations in the central Red Sea (Lat. 21°30N), and species of Mediterranean and Indian Ocean origin were represented, reflecting seasonal monsoonal influence. Low phytoplankton cell numbers accompanying high production rates suggest the significance of nanoplankton or picoplankton which were not enumerated. Production was high year-round, and averaged 390 gC m^-2 yr^-1, despite the virtual lack of nutrient additions from rainfall or land runoff or demonstrable upwelling. Highest nutrient levels followed the first seasonal peak of production. Biomass and production were seasonally bi- or tri-modal, with major peaks in December–February and June–August, 1977–1978. The first peak of production, populated by diatoms, occurred at the onset of seasonal stratification, but the second peak, populated by Trichodesmium spp., occurred at the height of seasonal stratification and lowest nutrient concentrations. There is no clear relationship between the timing of monsoon activity and the annual production cycle.     

Morphological variations in Ceratium egyptiacum in different natural habitats

A statistical study on the morphological variations of the dinoflagellate species Ceratium egyptiacum Halim was carried out in three distinct natural environments: The Red Sea, the Bitter Lake (Suez Canal), and the Mediterranean waters at Port Said, Egypt. Significant seasonal and regional variations were found in the parameters studied (length of the cell, transdiameter, length of the apical and right antapical horns). These variations are mostly attributable to variations in both the temperature and salinity of the environment. On the whole, it was found that high temperature tends to produce longer horns and smaller thecae, while low temperature produces larger cells with shorter horns; high salinity tends to intensify these effects. The right antapical horn is the most labile horn, and the transdiameter of the cell is the most stable parameter. It is suggested that these variations are directly related to flotation. The effect of the Bitter Lake as a unique natural environment (salinity 47) on plankton organisms has been evaluated; it is a function of time. The systematic consequences of the structural variations have been discussed; they are probably not genetic, and the resulting types are mere ecotypes of no immediate systematic consequence.